Fresh evidence emerged last night that Colin Powell, the US secretary of state, was so disturbed about questionable American intelligence on Iraq's weapons of mass destruction that he assembled a secret team to review the information he was given before he made a crucial speech to the UN security council on February 5.

Mr Powell conducted a full-dress rehearsal of the speech on the eve of the session at his suite in the Waldorf Astoria, his New York base when he is on UN business, according to the authoritative US News and World Report.

Much of the initial information for Mr Powell's speech to the UN was provided by the Pentagon, where Paul Wolfowitz, the US deputy defence secretary, set up a special unit, the Office of Special Plans, to counter the uncertainty of the CIA's intelligence on Iraq.

Mr Powell's team removed dozens of pages of alleged evidence about Iraq's banned weapons and ties to terrorists from a draft of his speech, US News and World Report says today. At one point, he became so angry at the lack of adequate sourcing to intelligence claims that he declared: "I'm not reading this. This is bullshit," according to the magazine.

Presented with a script for his speech, Mr Powell suspected that Washington hawks were "cherry picking", the US magazine Newsweek also reports today. Greg Theilmann, a recently retired state department intelligence analyst directly involved in assessing the Iraqi threat, says that inside the Bush administration "there is a lot of sorrow and anger at the way intelligence was misused".

The Bush administration, under increased scrutiny for failing to find Saddam Hussein's arsenals eight weeks after occupying Baghdad, yesterday confronted the damaging new allegations on the misuse of intelligence to bolster the case for war.

The gaps in the case against Saddam have become a matter for public debate only within the last few days. They have also become an issue of credibility for the CIA and the Bush administration as it begins to assemble a case against Iran and its nuclear programme.

Yesterday, a senior Bush administration official told reporters travelling with the president to the Evian summit that Washington was not alone in its pursuit of Saddam's arsenal.

"We have to remember that there's a long history of accusation of the weapons of mass destruction programmes in Iraq. A lot of what is unresolved about the Iraqi weapons of mass destruction programme comes from the United Nations, from Unscom, from Unmovic [teams of weapons inspectors] and, of course, from US and other intelligence," the official said.

The official also said that US forces in Iraq had not yet had the time to process the hundreds of documents captured since Saddam's fall, or track down the people with information on his weapons programmes.

On Friday, the CIA director, George Tenet, was forced to issue a statement denying the agency doctored intelligence reports.

"Our role is to call it like we see it, to tell policymakers what we know, what we don't know, what we think, and what we base it on. That's the code we live by," the statement said.

During a series of meetings at CIA headquarters last February, initiated by Mr Powell, the secretary of state was reported to have reviewed the intelligence reports on Saddam, his arsenal of chemical and nuclear weapons, and his possible links with al-Qaida. The ostensible purpose of the exercise, carried out over four days, was to decide which should be included in his address.

However, a common theme of the meetings was the failure of the CIA and other intelligence agencies to produce a convincing case against Saddam. Despite the increasingly belligerent statements from the administration's hawks, the CIA had disturbingly little proof.

Even more damaging, many of the assertions bandied about were based on reports that were speculative or impossible to corroborate - but seized on because they suited the agenda of the hawks in the administration. Ambiguities and nuance were left aside.

One claim from the original dossier that could not be proved involved the supply of sensitive software from Australia that would have allowed Baghdad to gather sensitive information about the topography of the US. However, the CIA could not establish for Mr Powell whether the software had been delivered to Iraq.

Although the issue of flawed CIA intelligence has caused concern about the agency's ability to gather evidence on potential threats to the US, it did not appear to have shaken the widespread belief that the war on Iraq was a just war.

"The day that I saw those nine and 10- year-old boys released from a prison, the day I saw the mass graves uncovered, it was ample testimony of the brutality and repressiveness of this regime," the Republican senator John McCain told ABC television yesterday. "It was the day that I believe our liberation of Iraq was fully vindicated."